(CNN) -- Sen. Elizabeth Warren was confronted by a voter in Sioux City on Saturday morning over her controversial decision to use a DNA test to prove her claims to Native American ancestry.
"I am not a person of color," the Massachusetts Democrat said. "I am not a citizen of a tribe. Tribal citizenship is very different from ancestry. Tribes -- and only tribes -- determine tribal citizenship, and I respect that difference."
Warren has addressed the backlash to her DNA test before, using similar language, but this -- the first question on her first full day of campaigning for the Democratic presidential nomination in Iowa -- underscored the lingering concerns over her decision.
The logic behind it, Warren explained, was simple. She grew up in Oklahoma, and like so many others in that region of the country, had been told of her family's Native American roots. The controversy traces back years, and more than one election, she said, recalling that her claim had been used against her by Republicans during her successful 2012 Senate campaign.
"My decision was to put it all out there," Warren said of the final calculation this time around.
The questioner, though, seemed less concerned about the offense the test caused to some Native Americans than its potential to fuel President Donald Trump's attacks .
"I can't stop Donald Trump from what he's going to do," Warren said. "I can't stop him from hurling racial insults. I don't have any power to do that," she added as an audience member yelled out, "Yes, you can!"
At that, Warren pivoted back to her campaign message, saying: "What I can do is I can be in this fight for all of our families. What I think 2020 is going to be about is not my family, it's about the tens of millions of families across this country who just want a level playing field."
Warren emerged as a leading critic of Trump during the 2016 presidential campaign, and he has responded -- repeatedly and throughout his presidency -- by mocking her Native American heritage and referring to her as "Pocahontas." But her choice to effectively engage the criticism from the President and others in October with a DNA test irked many Democrats and overshadowed her midterm message. (Warren would still win election to a second term in the Senate by nearly 25 percentage points.)
In an interview with Fox News after she announced her presidential exploratory committee earlier this week, Trump skewered Warren over the test and said he would "love to run against her."
Asked if he thought Warren believed she could defeat him in 2020, Trump said, "I don't know. You would have to ask her psychiatrist."
Before Warren spoke Saturday in Iowa, Judy Plank, a Democrat who had driven down from Le Mars, about a half-hour north, said she was concerned Warren had, in publicizing the results, set herself up for further ridicule from the President.
"It's just playing into his hands," Plank said. "It's getting onto his turf, and he knows how to handle his turf. And so I'm not sure she should have gotten into it, but anyway I hope she learned from it."
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